Mechanical Engineering - Research Publications
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ItemThe feasibility of downsizing a 1.25 liter normally aspirated engine to a 0.43 liter highly turbocharged engine(SAE Technical Paper Series, 2007)In this paper, performance, efficiency and emission experimental results are presented from a prototype 434 cm3, highly turbocharged (TC), two cylinder engine with brake power limited to approximately 60 kW. These results are compared to current small engines found in today’s automobile marketplace. A normally aspirated (NA) 1.25 liter, four cylinder, modern production engine with similar brake power output is used for comparison. Results illustrate the potential for downsized engines to significantly reduce fuel consumption while still maintaining engine performance. This has advantages in reducing vehicle running costs together with meeting tighter carbon dioxide (CO2) emission standards. Experimental results highlight the performance potential of smaller engines with intake boosting. This is demonstrated with the test engine achieving 25 bar brake mean effective pressure (BMEP). Results are presented across varying parameter domains, including engine speed, compression ratio (CR), manifold absolute pressure (MAP) and lambda (λ). Engine operating limits are also outlined, with spark knock highlighted as the major limitation in extending the operating limits for this downsized engine.
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ItemCompression ratio effects on performance, efficiency, emissions and combustion in a carbureted and PFI small engine(SAE Technical Paper Series, 2007)This paper compares the performance, efficiency, emissions and combustion parameters of a prototype two cylinder 430 cm3 engine which has been tested in a variety of normally aspirated (NA) modes with compression ratio (CR) variations. Experiments were completed using 98-RON pump gasoline with modes defined by alterations to the induction system, which included carburetion and port fuel injection (PFI). The results from this paper provide some insight into the CR effects for small NA spark ignition (SI) engines. This information provides future direction for the development of smaller engines as engine downsizing grows in popularity due to rising oil prices and recent carbon dioxide (CO2) emission regulations. Results are displayed in the engine speed, manifold absolute pressure (MAP) and CR domains, with engine speeds exceeding 10,000 rev/min and CRs ranging from 9 to 13. Combustion analysis is also included, allowing mass fraction burn (MFB) comparison. Experimental results showed minimum brake specific fuel consumption (BSFC) or maximum brake thermal efficiency (nTH) values in the order of 220 g/kWh or 37% could be achieved. A maximum brake mean effective pressure (BMEP) of 13 bar was also recorded at 8000 rev/min.
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ItemCombustion system development and analysis of a carbureted and PFI normally aspirated small engine(SAE Japan & SAE International, 2009)This paper focuses on the combustion system development and combustion analysis results for a normally aspirated 0.43 liter small engine. The inline two cylinder engine used in experiments has been tested in a variety of normally aspirated modes, using 98-RON pump gasoline. Test modes were defined by alterations to the induction system, which included carburetion and port fuel injection fuel delivery systems. The results from this paper provide some insight into the combustion effects for small cylinder normally aspirated spark ignition engines. This information provides future direction for the development of smaller engines as oil prices fluctuate and CO2 emissions begin to be regulated. Small engine combustion is explored with a number of parametric studies, including a range of manifold absolute pressures up to wide open throttle, engine speeds exceeding 10,000 rev/min and compression ratios ranging from 9 to 13. Combustion system optimization through compression ratio development enabled the engine to achieve 37% brake thermal efficiency and 13 bar brake mean effective pressure. Hence, the test engine performance and efficiency results demonstrate that smaller bore engines can match or exceed typical larger bore engines found in passenger vehicles. However, this was only possible after compression ratio optimization to compensate for the higher levels of dissociation, friction and heat losses associated with the small cylinder size.
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ItemCombustion system development and analysis of a downsized highly turbocharged PFI small engine(SAE Japan & SAE International, 2009)This paper provides some insight into the future direction for developing smaller capacity downsized engines, which will be needed to meet tight CO2 targets and the world’s future powertrain requirements. This paper focuses on the combustion system development and combustion analysis results for a downsized 0.43 liter highly turbocharged engine. The inline two cylinder engine used in experiments was specifically designed and constructed to enable 25 bar BMEP. Producing this specific output is one way forward for future passenger vehicle powertrains, enabling in excess of 50% swept capacity reduction whilst maintaining comparable vehicle performance. Previous experiments and analysis have found that the extent to which larger engines can be downsized while still maintaining equal performance is combustion limited. Hence, small engine combustion is explored over a number of parametric studies, including a range of manifold absolute pressures up to 270 kPa, engine speeds exceeding 10,000 rev/min and compression ratios ranging from 9 to 13. Experimental results indicate that small engine combustion hurdles can be overcome to reliably extend the specific output to 25 bar BMEP. This is believed to be the highest recorded specific output for a non-intercooled small spark ignition PFI engine operating on pump gasoline. However, the boosted combustion effects illustrate that the thermal efficiency is highly dependent on the combustion efficiency, which deteriorates rapidly if uncontrolled combustion, specifically knock in the end-gas region is encountered. However, with this combustion system design strategy, potential drive cycle fuel consumption improvements in excess of 20% are still achievable.